"The Neverending Story" is one of the best works of children's literature I know - and I do mean literature in the most profound way. I mean, one of its central themes is the Thelema (of Aleister Crowley) fame, and there's a lot more depth than what you'd find in, say, the average Harry Potter book.

It also has plenty of inspiration for fantastic #ttrpg scenery. But do me a favor and read the book - ignore the rather disappointing movies.